This applies to the '76 quarter, half and dollar. There are spaces for 76-P, 76-D, 76-S, 76-S 40% proof and 76-S 40% BU. Now you can get the PDS from the usual sources. The S 40% proof from the 3 coin silver set. My questions is, where do you get the S 40% BU? And why would an S not be in a proof set?